trim and extend in diferent Z-value

Hi there

I have a problem with trim and extend command. If lines have Z coordinates diferent than 0 and I use trim or extend command, new trimed or extended ends go to the 0 Z value.

Is there way how to preserve them in the same Z like before thise commands? Of course I can change local UCS, but its a little bit longer way.

Thanks for an answare

J.